Submission #1099035

#	Time	Username	Problem	Language	Result	Execution time	Memory
1099035		LIA	Flight to the Ford (BOI22_communication)	C++17	Compilation error	0 ms	0 KiB

communication

#include <bits/stdc++.h>
using namespace std;

#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cstdarg>
#include <cassert>
#include "communication.h"

void __attribute__((noreturn)) __attribute__((format(printf, 1, 2))) result(const char *msg, ...);

void encode(int N, int X);
pair<int, int> decode(int N);

namespace {
    enum { ENCODE, DECODE } current_phase;
    int N, X;
    vector<int> signals;
    size_t cursor = 0;
    bool flipped = false;
}

int send(int s) {
    if (current_phase == DECODE || (s != 0 && s != 1))
        result("Invalid send.");

    printf("send(%d) -> ", s); fflush(stdout);
    int answer;
    if (scanf("%d", &answer) != 1 || (answer != 0 && answer != 1))
        result("Invalid reply to send.");

    bool flipped_now = (s != answer);
    if (flipped && flipped_now)
        result("Invalid reply to send");
    flipped = flipped_now;

    signals.push_back(answer);
    if (signals.size() > (size_t)250)
        result("Looks (and smells) fishy.");
    return signals.back();
}

int receive() {
    if (current_phase == ENCODE) result("Invalid receive.");
    if (cursor >= signals.size()) result("Assistant waiting for Godot.");
    int r = signals[cursor++];
    printf("receive() -> %d\n", r);
    return r;
}

int main() {
    if (scanf("%d %d", &N, &X) != 2 || X < 1 || X > N)
        result("Invalid input.");

    current_phase = ENCODE;
    encode(N, X);
    current_phase = DECODE;
    auto r = decode(N);

    if (r.first < 1 || r.first > N || r.second < 1 || r.second > N)
        result("Invalid answer.");

    if (r.first == X || r.second == X)
        result("Correct: %d signals sent.", (int)signals.size());
    else
        result("Wrong answer.");
}

void encode(int N, int X) {
    if (X == 1) {
        send(0);
        send(1);
    } else if (X == 2) {
        send(1);
        send(0);
    } else if (X == 3) {
        send(1);
        send(1);
    }
}

pair<int, int> decode(int N) {
    int first_bit = receive();
    int second_bit = receive();

    if (first_bit == 0 && second_bit == 1) {
        return {1, 1};
    } else if (first_bit == 1 && second_bit == 0) {
        return {2, 2};
    } else if (first_bit == 1 && second_bit == 1) {
        return {3, 3};
    }

    return {1, 2};
}

Compilation message (stderr)

/usr/bin/ld: /tmp/ccBuCgF8.o: in function `send(int)':
interface.cpp:(.text+0x70): multiple definition of `send(int)'; /tmp/ccnlY5e8.o:communication.cpp:(.text+0xf0): first defined here
/usr/bin/ld: /tmp/ccBuCgF8.o: in function `receive()':
interface.cpp:(.text+0x100): multiple definition of `receive()'; /tmp/ccnlY5e8.o:communication.cpp:(.text+0x0): first defined here
/usr/bin/ld: /tmp/ccBuCgF8.o: in function `main':
interface.cpp:(.text.startup+0x0): multiple definition of `main'; /tmp/ccnlY5e8.o:communication.cpp:(.text.startup+0x0): first defined here
/usr/bin/ld: /tmp/ccnlY5e8.o: in function `receive()':
communication.cpp:(.text+0x66): undefined reference to `result(char const*, ...)'
/usr/bin/ld: communication.cpp:(.text+0x74): undefined reference to `result(char const*, ...)'
/usr/bin/ld: /tmp/ccnlY5e8.o: in function `send(int)':
communication.cpp:(.text+0x1fa): undefined reference to `result(char const*, ...)'
/usr/bin/ld: communication.cpp:(.text+0x208): undefined reference to `result(char const*, ...)'
/usr/bin/ld: communication.cpp:(.text+0x216): undefined reference to `result(char const*, ...)'
/usr/bin/ld: /tmp/ccnlY5e8.o:communication.cpp:(.text+0x224): more undefined references to `result(char const*, ...)' follow
collect2: error: ld returned 1 exit status